1. Field of the Invention
The present invention is directed to an ultrasonic liposuction device and a method of using the same to remove unwanted tissue or fat from a mammalia body. More particularly, the present invention is directed to an ultrasonic liposuction device which includes a push rod which vibrates at a predetermined frequency, and which in turn drives a probe or cannula at a predetermined frequency and amplitude in order to assist in the cavitation, emulsion and removal of fat tissue from a patient's body.
2. Background and Description of the Related Art
During the past 20 to 25 years, liposuction or "suction assistant lipectamy" has become a widely accepted procedure for removing localized areas of fat tissue which are normally unresponsive to diet or exercise. Regions of the body which are frequently treated by liposuction include: the waist ("love handles"); buttocks; thighs ("saddle bags"); ankles; lower legs; upper arms and the jowl area of the face. Liposuction has become a major source of revenue for the cosmetic industry. In conventional liposuction the removal of unwanted fat tissue is typically accomplished by inserting a narrow metal probe or cannula through an incision in the patient's skin and moving the probe back and forth within the patient's body to loosen the fat tissue. A vacuum is applied to suck out fat tissue that the cannula is in contact with. The procedure normally results in long tubular cavities in a wattle like pattern in the patient's fatty tissue area. The cannula generally has a rounded end and a small opening along the side or at the top in order to allow the fat particles to be removed. By manipulating the tube in and out of the area, a large amount of fatty deposit may be removed and the subject area is flattened, thereby approving the appearance the patient upon which the procedure is being performed.
Although the aesthetic benefits of conventional liposuction are well documented, the conventional procedure described above is normally very traumatic and usually accompanied by severe bruising of the treated area and the surrounding area. In fact, the bruising may be quite extensive due to the disruption of the small blood vessels which are attached to the fat globules being removed. Blood loss is also a concern for patients due to the fact that conventional liposuction devices are unable to differentiate between fat and connective tissue or blood vessels, the tissue is being ripped from the body was connective tissue and/or blood vessels.
In addition to the trauma to the patient, the physician generally uses a great deal of energy due to the force required to move the probe in and out of the area being treated. This force is necessary on the physician's behalf because the in and out movement of the probe shears off fat tissue particles. The fat tissue particles sheared off are drawn into the tube and out of the body by vacuum. The reason a blunt end probe or cannula is used is that the blunt end of the cannula pushes the larger blood vessels and nerves out of the way thereby causing less damage or trauma to the patient.
As can be seen above, conventional liposuction and the devices used therein have well documented undesirable side effects, including, unwanted trauma to the patient and physical exhaustion and tiring of the surgeon. In response to these disadvantages, ultrasonic lipectomy or liposuction procedures have been developed which rely on an ultrasonic transducer to vibrate the probe to reduce the effort of the surgeon and reduce the trauma to the patient. Generally, in these procedures the suction probe is connected to an electromechanical transducer of either magnetostrictive or electrostrictive design. Upon activation of the transducer longitudinal vibrations are sent up the probe and the distal end of the probe is turned into a vibrating wand which serves to liquefy (emulsify or cavitate) the fat that comes in contact with it either through heat (U.S. Pat. No. 4,886,491 which is hereby incorporated herein by reference in its entirety) or cavitation (U.S. Pat. No. 5,419,761 which is also hereby incorporated herein by reference in its entirety). The vibratory effect of the probe allows the surgeon to move the probe through fatty tissue very easily. The fatty emulsion or liquid that results from melting or cavitation is removed from the body, much in the same way as standard liposuction technique, that is, by way of as suction source and a collection bottle. The level of vacuum needed to remove the fat from ultrasonic liposuction is substantially less than that needed in the standard liposuction procedure due to the fact that the fat is liquefied or emulsified. The liquification of the fatty tissue surrounding the distal end of the probe allows the probe to be easily inserted and retracted from the body, and as a consequence reduces the trauma to the patient and reduces the effort needed by the surgeon. Obviously one of the benefits of ultrasonic liposuction is less fatigue on the part of the surgeon which allows him to be more efficient and more alert and allows him to perform more procedures in a day. In addition, less bleeding has been seen during the use of these procedures and the ultrasonic vibration of the probe has shown to have a cauterizing effect on small blood vessels.
U.S. Pat. No. 5,527,273 and U.S. Pat. No. 5,181,907 both of which are hereby incorporated by reference in their entirety outline several of the advantages offered by ultrasonic liposuction. Ultrasonic liposuction devices developed to date require cannulas or probes which are specifically designed to resonate or translate at desired frequencies. The probes are vibrated at ultrasonic frequencies in the range of 16,000 to 60,000 cycles per second. Therefore, the probes that are being used are subject to stresses and fatigues not encountered by passive probes used in conventional liposuction procedures. Additionally, the ultrasonic liposuction probes generally must be designed to provide sufficient multiplication of the amplitude input provided by the transducer which drives it.
It is known that a particularly effective probe for ultrasonic liposuction is a hollow cylindrical probe with a bullet shaped tip on the distal end. The tip can be welded or otherwise affixed to the probe. Both probe and tip can be manufactured from a variety of acoustically conductive metals, including cold-rolled steel, titanium and aluminum. In presently known devices, the probe and tip are manufactured from the same materials, or from very similar materials, to ensure effective propagation of the ultrasonic waves all the way to the tip of the probe. Propagation of the waves to the distal tip of the probe is desirable, because this causes the tip of the probe to be able to melt and emulsify fat, facilitating insertion of the probe into the fatty tissue.
However, there is a disadvantage sometime associated with an ultrasonic probe having an acoustically conductive tip. For instance, when the probe has been inserted into the fatty tissue near the skin or the peritoneum, resistance can be met. When resistance is met, the wattage at the tip increases, and it can increase to the point of damaging the skin or the peritoneum. During such manipulations, the heat generated at the tip of the probe may be in excess of the heat reasonably required for the melting of fat. In other words, if care is not exercised, the tip may be hotter than it needs to be, and the result can be burning of tissues, damage of muscles or blood vessels, and even penetration of membranes, such as the skin or the peritoneum. Therefore, while the bullet shaped tip of acoustically conductive material, it can be very beneficial during penetration, it can under certain circumstances, also be detrimental.
Relying on the probe as the vibrational element to transmit the vibration or multiply the vibration provided by the input acoustical source also results in numerous disadvantages when performing ultrasonic liposuction. Straight cylindrical probes normally do not provide gains for ultrasonic vibration and accordingly, the probes must be driven at the high input amplitudes necessary for tissue liquefaction. This causes high stress concentration at node points or points where the vibratory motion and the standing wave are zero. When stress is high, material heating problem can occur. The problem is that the temperature of the probe at the stress know points elevates and again can cause tissue burning or charring when in contact with the tissue of the body or the patient in which the liposuction application is being performed. Obviously, this major drawback of using laboratory elements must be avoided since the probes are inserted deeply in the body and burning or scarring of the lower levels epidermis or other tissues or organs may result.
In practice, the probes described heat significally at the nodal regions and are prone to fracture at high amplitudes and have a tendency to break into transverse motion wherein the tips of the probes causing fracturing and the possibility of leaving pieces of metal in the body of the patient in which the operation is being performed.
The necessity to construct the probe out of a material which transmits the vibratory amplitude of the electromechanical transducer also provides a number of disadvantages to a field of ultrasonic liposuction. Generally, the probes are limited in construction a titanium or titanium alloy due to the expansion/contraction characteristics of titanium and can be very fragile in design in that a risk of loss of amplitude or frequency may occur with minor probe damage such as scratching or general wear so that the vibrational frequency of the probe is out of tune of that desired or indicative by the electromechanical transducer. Additionally, the working end of the probe must be larger than the body of the probe in order to accommodate the aspiration channel and maintain the ultrasonic resonance.